Нужно поставить их в правильной форме (past simple или past perfect) 16  he (be) an american citizen for 20 years when the war (break out)  17  he (say) he (spend) the last 15 years of his life exploring the world  18  i (not can) buy the record because i (lose) the money  19  i (not go) to the museum with my class because i (be) there before  20  when we (buy) the house, it (be) empty for several years

He was an American citizen for 20 years when the war  had broken out.
He said he had spent the last 15 years of his life exploring the world. 
I couldn't buy the record because I had lost the money
I didn't go to the museum with my class because I had been there before
When we had bought the house, it was empty for several years 
Не уверена в правильности, но, как говорится чем смогла)